Hypoplastic Nasal Bone

Any mommies gt a 'hypoplastic nasal bone' diagnosis during 20week scan before but gave birth to normal baby? My measurement was 3.4mm and its a soft marker for Downs. Other than that, baby is healthy (heart, kidney etc.) Dr recommended Amniocentesis test which i opt out due to risk factor. Please share and feed me with more infos, nothing much and detailed through Google... And it's stressing me.